The integration of Environmental, Social, and Governance (ESG) factors into corporate strategies has emerged as a critical determinant of firm performance in global financial markets. This study investigates the multidimensional relationship between ESG practices and corporate financial performance among ASEAN firms listed in the Nikkei Asia 300 Index over the period 2018–2022. Drawing on stakeholder theory and corporate governance frameworks, the research employs a structured analytical approach to examine how ESG disclosures influence profitability, market valuation, and financial stability. The findings indicate that ESG integration positively correlates with financial performance, particularly in firms operating within environmentally sensitive sectors, although variations exist across governance structures and disclosure intensities. The study contributes to the growing body of ESG literature by providing region-specific empirical insights and highlights the importance of institutional and regulatory environments in shaping ESG outcomes. Limitations related to data heterogeneity and measurement inconsistencies are acknowledged, with recommendations for future longitudinal and sector-specific studies.